China DOS Union

Most books say that msdos.sys must be larger than 2K, and that's also why there are so many x's in msdos.sys. But after I deleted some of the x's, I found that it could still boot. At that point msdos.sys was only a little over 300 bytes. I don't know why.

The reason msdos.sys has to be over 2K is to prevent MSDOS。SYS from being mistakenly identified as
a virus under DOS. If you don't have DOS antivirus software installed, and MSDOS。SYS wasn't deleted,
then of course there won't be any problem.

Not very sure. msdos.sys is relatively important in win98. It must be over 1024 bytes, (that means over 1K, seems like not over 2K). (MSDOS.SYS needs to be >1024 bytes). It provides some parameters to regulate how win98 starts, whether to start Windows and so on, I guess. (There are detailed explanations of the meaning of the various parameters in msdos.sys in many places, and there are also some on this forum.) If you're just making a win98 boot disk, then msdos.sys doesn't have much of a role. Generally, it is only 6 bytes. (Some are even just 2 bytes.) It's also okay if you delete it, you just won't be able to enter the win98 Windows screen, and can only enter pure DOS.

KO already explained it very clearly. As for why msdos.sys has to be larger than 1024 bytes, it's always been a question. There still isn't any related documentation, and Microsoft hasn't explained it either. Maybe MS is just being deliberately mysterious. Actually, MSDOS.SYS is no longer important once you're in WINDOWS. Even if it is smaller than 1024K, windows won't have any problems. For configuration instructions about msdos.sys, please see my repost WIN9X……http://www2.zzu.edu.cn/ie/newdos/dispbbs.asp?boardID=3&ID=469

I've also read articles on this. Supposedly MSDOS has to be larger than 1K for compatibility with some old DOS programs. As for DOS7.1, it really doesn't matter. On my floppy disk its length is 0.

I once saw this in Computer News. It said that in older antivirus software,
under DOS, files that were too small would be mistakenly identified as viruses.
And then deleted.
But MS。DOS itself doesn't need much content. So they added these *'s.
As for whether it's true, it seems nobody has really verified it.
Maybe you could find an antivirus program so old it's got no teeth left,
delete the *'s from MSDOS, then run the antivirus software under DOS.
And see whether it deletes MSDOS。